<?php

function getRandomString($len, $chars=null)  
{  
    if (is_null($chars)) {  
        $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";  
    }  
    mt_srand(10000000*(double)microtime());  
    for ($i = 0, $str = '', $lc = strlen($chars)-1; $i < $len; $i++) {  
        $str .= $chars[mt_rand(0, $lc)];  
    }  
    return $str;  
} 

/**
 * 获取用户ip
 * @param  integer $type [description]
 * @return [type]        [description]
 */
function get_client_ip($type = 0) {
    $type       =  $type ? 1 : 0;
    static $ip  =   NULL;
    if ($ip !== NULL) return $ip[$type];
    if(isset($_SERVER['HTTP_X_REAL_IP'])){//nginx 代理模式下，获取客户端真实IP
        $ip=$_SERVER['HTTP_X_REAL_IP'];     
    }elseif (isset($_SERVER['HTTP_CLIENT_IP'])) {//客户端的ip
        $ip     =   $_SERVER['HTTP_CLIENT_IP'];
    }elseif (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {//浏览当前页面的用户计算机的网关
        $arr    =   explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
        $pos    =   array_search('unknown',$arr);
        if(false !== $pos) unset($arr[$pos]);
        $ip     =   trim($arr[0]);
    }elseif (isset($_SERVER['REMOTE_ADDR'])) {
        $ip     =   $_SERVER['REMOTE_ADDR'];//浏览当前页面的用户计算机的ip地址
    }else{
        $ip=$_SERVER['REMOTE_ADDR'];
    }
    // IP地址合法验证
    $long = sprintf("%u",ip2long($ip));
    $ip   = $long ? array($ip, $long) : array('0.0.0.0', 0);
    return $ip[$type];
}